A D-class amplifier that can suppress noise generated when a D-class amplification operation is started/stopped. When a D-class amplification operation is started/stopped, the pulse widths and pulse interval of output signals Pout1, Pout2 are gradually changed, so it is possible to prevent a large variation in the signal fed as a differential signal of output signals Pout1, Pout2 to the load, and it is possible to reduce noise. That is, by gradually changing the pulse interval while keeping the pulse widths of output signals Pout1, Pout2 constant, it is possible to suppress variation in the relatively high frequency component corresponding to the component of the pulse signal. Also, by gradually changing the widths of output signals Pout1, Pout2 while keeping the pulse interval constant, it is possible to suppress variation in the relatively low frequency component corresponding to the average value of the pulse signal.